Multispeed induction-motor



C. MACMILLAN.

I MULTISPEEDI INDUCTION MOTOR.

APPLICATION FILED MAY 31, 1917. 1,356,934. Patented Oct. 26, 1920.

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C. MACMILLAN.

MULTISPEED INDUCTION MOTOR.

APPLICATION FILED MAY3I,1917.

Patented Oct. 26, 1920.

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Inventor Campbell Macmillan,

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Patented Oct. 26, 1920.

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MULTISPEED INDUCTION MOTOR.

APPLICATION FILED MAY31, 1917.

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MULTISPEED INDUCTION MOTOR.

APPLICATION FILED MAY 31. 1917.

356,934. Patented Oct. 26,1920.

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UNITED STATES PATENT OFFICE.

CAMPBELL MACMILLAN, 0F SCHENECTADY, NEW YORK, ASS IGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

MULTISPEED INDUCTION-MOTOR.

Specification of Letters Patent.

Patented Oct. 26,1920.

Application filed May 31. 1917. Serial No. 171,915.

duction motors and has for its object the provision of an improvedmulti-speed inductlon motor. My invention more particularly relates tomulti-speed induction mo-- tors of the type described in my copendingapplication for Letters Patent of the United States, Serial No. 171,916,filed May 31, 1917. In this connection, the object of my invention is toprovide an induction motor having a primary winding with simplifiedconnections for producing substantially sinusoidal or balanced primarymagnetic fields of different pole numbers when connected to polyphasesystems of energy distribution of different numbers of phases. Otherobjects of the invention will be brought out in the course of the'following description.

I have described in my aforementioned application a multi-polarinduction motor having a primary winding arranged to produce primarymagnetic fields of different pole numbers when suitably connected topolyphase systemsof energy distribution of different numbers of phases.I particularly described a primary winding arranged to produce primarymagnetic fields of either 72 or 2% poles when suitably connected to apolyphase system of three-phase electromotive forces and a'primarymagnetic field 3n 0f 3 polyphase system of quarter-phase electromotiveforces. The particular aim of my present invention is to provide a moresimple arrangement for effecting the necessary circuit connections insuch a combination poles when suitably connected to a comprising asource of polyphase energy phase when the primary winding is arrangedfor one pole number to a common neutral, and, considering the oppositeends of all coil-sections, to connectthose coil-sections which are inthe same phase when the primary winding is arranged for the second polenumber to a common neutral. The common connections at one end of thecoils sections then serve as terminals for one pole number of theprimary winding and the common connections at the other end form acomplete set of neutralor Y-points, while for the other pole number thelatter common connections serve as terminals and the first mentionedcommon connections form a com-' plete set of neutral points.

The novel features of the invention which I belleve to be patentable aredefinitely set .forth in the appended claims. Theprinciple of theinvention, together with the construction and mode of operation ofinduction motors and systems embodying the same, will be best understoodfrom the following description taken in conjunction with theaccompanying drawings, in which:

Figure 1 is a diagrammatic assembly of a system of electric shippropulsion embodymg the present invention; Fig. 2 is an explanatorylegend-diagram; Fig. 3 is a diagram of the electrical connections of thesystem of Fig. 1; Figs. 4.- and 5 are explanatory vector diagrams Figs.6 and 7 are explanatory diagrams of the different connections of themotor shown in Figs. 1, 2 and 3; Fig. 8 is a diagrammatic view of amodified form of the invention; Fig. 9 is a diagrammatic view of afurther modification of the invention; Figs. 10, 11 and 12 are explanatory diagrams of the difi'erent connections of the primary windingof the motor represented in Fig. 9; Fig. 13 is a diagrammatic view ofanother modification of the invention; and Fig. '14 is an explanatorydia ram.

he present invention is of particular ad- Vantage in electric systems ofship propulsion, and in Fig.1 I have illustrated such a systemcomprising an elastic-fluid turbine 15 directly coupled to analternating current generator 16. A multi-speed induction motor 17 hasits rotor mounted on the shaft 18 of one of the ships propellers 19. Itwill of course be understood that the entire equipment will generallyconsist of a plurality of ropellers and induction motors, and usuali;will include two or more turbine-driven' generators 15-16. Thepropellet-tithing motel" 1? is o'tesigmedi toe poie= changing in ordertoprovisie two efiicient speed ranges of navigation. eeeordenee with mymeseht invention, the Winding CU: the motes 1? is prone? with verysimple connections for pemiuemg pr msry magnetic fiehts o ciifierentpoie numbers when supphed 0; th with poiyohese oi 1 tion of em;

The primery winding of the so-eeiieai three-phase meter usueiiy Woundsix-phase with is obteh oil by otwo phase-belts 1B which U current flowseietiwiy pieced 180 ing to each at the t "a; 1 of sup iy, The belts aredis sti'ieei degeees and called a 66 six-12h Such e. Winding is sentedby row U:

t, e of 2, Where it 6 g0. The ietters pho-se-beits or eat phase A andtiveiy opposite in (2 degrees out of ph the eorrespontiing f ,SS-o pheseB, emit e e the eeriespoedihg phase-belts connected to phase C, Ah ofthe phase-h the same phase may electrically connected together anysuitable mealtimes for example, iii series, in pereiiei or: partly inseries and pertiy pg eliei, es W312i he omteestooii by those s2.

the es 7 The seeomi i resents the errengemeet of the sits connected toprimary Whese" ee has the same numhei: of e- 3 belts of then-pole W Inthe showings, g ere, therefore, the phese heits e: n-poie v n Winding nm 1.1 v. me if trfieei degrees out of phase with seeeeee The i'eletivepitch of the primary coiis v J. .L 4 s q 4?. go ee-oeh, must undergo inpessig x one arrangement to o1. 'lhe w 4.1. :2 Q i posse-belts whichundergo eel mange in passing i nt to the other may be ei CO1 in e singlegimp, emi it W- s from eii'inspeetioe Fig. 2

Wiii be twelve of such T3853 designated by the legends be hues to mheetethe p I H1 their connections W ie numbers of primary .1 iengeci. Thus, ais eoniieet ese for the n-poie arrangement 5 the positive terminal ofEehese 1 for the q -poie arrangement; group 5g is connected phase B soas to carry ce ent 6Q eieethe oureent in phase-halt a for the n-poiearrangement enci to the positive terminoi of phase Q1 '50? the phase Cso as to deny current 120 eieetrieei oiegrees out of phase with thecurrent iii phase-belt a for the 'vpole arrangement ens to the negativeterminei oi phase P foe 3e J 1 e =peie emengemeeo, ELLE; so on tnteeminei A, the coii-seetioes 5 end here connected to the commontei'miiiei B and the coil-sections e and e we co men terminaleo1i-seet1e ewengementg group 5 is GGBHGOEQCi '4 when quarter-phasecurrents are supplied to the terminals P, R1] and Q, the primary windingwill be arranged as a -pole, quarter-phase, three-circuit diametricalwinding. These circuit arrangements Wlll be more clearly seen after adiscussion of Fig. 3.

Lhe electrical connections of the system of Fig. 1 are shown in Fig. 3.p The primary winding of the motor is divided into twelve circuits orgroups, just as explained in con- 'nection with Fig. 2. These groups aredesignated by the ame legends as in Fig.2. The common terminals orneutrals are likewise designated by the same reference letters as inFig. 2. The armature winding of the generator 16 has four coil-sections40, 41, 42 and 43, which are 60 electrical degrees apart,

and four coil sections 4.4, 15, 46 and 47,

nated by the same reference characters as the corresponding coilsectionsof Fig. 3. The connections oi the twelve groups of the primary windingof the motor for this position of the switch 21 are shown in Fig. 6.When the switch 21 is thrown to its upper position, the armaturecircuits of the generator are connected as a two-circuit inde pendent.quartenphase winding to the quarter-phase terminals P, F, Q and Thevector diagram of the generator winding for this connection isrepresented in Fig. 5, and the connections of the primary winding of themotor shown in Fig. 7

It will be observed that the switching mechanism for polie-changingbecomes very simple by the use or" my present invention. Only seventerminals are brought out from the multi-polar induction motor. Thequarter-phase terminals are provided with a reversing switch 22, sincein ship propulsion reversal will oniy be carried out with the low speedpolar arrangement, that is with 3% -poles.

In Fig. 8 of the drawings, I have shown a multi-polar motor adapted tobe supplied with polyphase systems of energy distribution of three andsix phases. Following the procedure outlined in Fig. 2, it will 'beevident that in the most general case of n and m primary magnetic poles,the primary windingmust be divided into eighteen circuits or groups. Thephase-belts for the three-phase arrangement I will designate a .Z), cand for the six-phase arrangement a, I), c, 6 b, E, and the eighteengroups are designated by characteristic legends following the systemused in-Figk2. All of the phase-belts a for the -n-pole three-phasearrangement are connected at one end to a common terminal A, andsimilarly with respect to phase-belts Z) and 0. The other ends of thephase-belts are connected to six terminals so that the same phase-beltsfor the m-pole six-phase arrangement are connected to the sameterminals. The motor, accordingly, has only nine terminals. The armaturewinding 26 of the supply generator is delta connected for three-phaseand diametrical for six-phase. A single switch 27 with six double-throwblades effects the necessary changes in the enerator and motor circuitsfor changing rom n to m poles, or vice'versa. When this switch is in itslower position, the generator is three-phase delta-connected to themotor terminals A, B and C and the primary winding of the motor producesa primary magnetic field of n-poles. lVhen the switch 27 is in its upperposition, the generator is connected to deliver six-phase electromotiveforces to the motor terminals a, I), c, d, b, and E, and the primarywinding produces m poles.

The multi-polar motor or my present invention may have a secondarywinding of any suitable t pe. The simplest type of secondary win ingwould be a low resistance squirrel cage winding, but for installationswhere speed control or increased torque is desiredthe secondary windingmay be phase-wound and arranged for connection to an externalresistance. Where increased torque for particular conditions ofoperation are required, as for reversing in ship pro pulsion, a doublesquirrel cage secondary winding may be of advantage, as explained inLetters Patent of Ernst F. W. Alexanderson, No. 1,215,095, patented Feb.6, 1917. Increased torque of the motor may also be obtained in themanner described in my copending application for Letters Patent oi theUnited States, Serial No. 171,917, filed May 31, 1917. Such amodification of the present invention is illustrated in Fig. 9.

The row of short heavy vertical lines in Fig. 9 represents the centersof coil-sections or phase-belts of the primary winding of a multi-speedinduction motor, as described in connection with Fig. 2. In the motor ofFig. 9, n is equal to 16 and is equal to 24.

In addition, the coil-sections of this winding are arranged to beconnected as a 32- pole threephase primary winding. The arrangement ofthe coil-sections for this 32- pole connection is represented by thelast row of legends a, b, a, a, etc.

The polyphase systems or energy distrihution otdiherent nnmhers atphases are produced by a generator whose armature winding 22 is athree-phase star-connected winding. One phase winding of the generatoris divided into two sections 60 electrical degrees apart. The circuitsand connected'in diametrical independent circuits for quarter-phase. Thegenerator switch 23 is a five-unit doulole-throw switch and in changingthe generator circuits fnom three-phase to quartenphasealtersthe voltageper phase of the generator in the-ratio of l to 0.71. In other words,the terminal voltage of the generator when tarnishing quarter-phaseelectromotive forces is 71% tit? of its terminal voltage,2 wheninrnishing three-phase electroniotive tor-cos.

In accordance withthe principle of my i present invention, all: ot thephase-helts o with respect to the 32-pole arrangement are connected atone end to a common terminal A, and the phaseheltsh and c are similarlyconnected to common terminals B and C, r spectively. Considering now"the Qt-pole quarter-phase arrangement, all of the basebelts areconnected at their other on s to a common terminal 1?, andall oi"thephasehelts 37 are similarly. connected to a common terminal P. Thecommon terminal Q is made up of three terminals a, ii, a, and the commonterminal is similarly made up of three other terminals d, h, c. A loanunit double-throw switch 24: is provided for connectin the'threeterminalso, h, c of terminal Q 6;, l5, c of terminal Q together when theswitch is in its lower position. When the switch is in its upperposition, it connects the two terminals 6 and a together, and similarlythe two terminals 5 and h and E and c.

A. second motor switch 26 isprovided. In its right-hand position thisswitch connects the three-phase suoioly system to the motor terminals A,1%, and in its lefthand position it connects the three-phase supplysystem to the notor terminals 5/ h 5'.

he manipulation of the switches 23, 24. and 26 to eilect the din erentoperating conditio'ns of the system is as follows: For capolequartenphase operation or the motor the switch 23 1S thrown to itsle'lthand the motor circuits for 32 active. ciated with the eleventerminals of the motor together and the three terminals incense ation ofthe motor, the generator switch 23 is thrown to its right-hand position,and the motor switches 24 and 26 are thrown to their lower andright-hand positions, respectively. 'lhe groups of the motor winding arethen arranged as indicated in Fig. 11. For the 32-pole three-phaseoperation oi the motor, the generator switch 23 is in its righthandposition, and the motor switches 24 and 26 are in their upper andleft-hand positions, respectively, he arrangement of poles is shown inFig. 12. It will he ohserved that these three polar arrangements areobtained with only eleven motor terminals. The twelve groups of themotor winding are designated in liigs. l0, l1 and 12, by characteristiclegends op, =1:

cg, etc., to designate the changes iii-the connections of the groups forthe three dih'erent olar arrangements. These characteristic egends arederived icom the legends of Fig. 9, as will he clearly understood inView of preceding explanations i In accordance with the invention of myalorementionedap lic'ation Serial l lo. 171,917, the primary winding ofthe motor represented in Fig. 9 is divided into two components such thatwhen one component is disconnected fromthe source 01 supply alternatesections emhracing 4:, 6 or 8 poles, according as the primary 'windin isconnected for 16, 2d or 32 poles, are i is or in- To this end switches25 are assoso as to disconnect these alternate sections of the primarywinding from the source of supply. A compound or double secondarywinding is provided, one section oi which is of low resistance and theother section of high resistance. in Fig. 9 of the drawings, 1 haveshown a high resistance squirrel 'cage'winding 20 and a low resistancesecondary winding 31 arranged so that when alternate sections of theprimary winding Lido tors corresponding to idle sections of the primarywmding are included by transferiner action as a part of the secondarying of the motor.

The coils of the winding 31 are connected to two sets of collector ringsand 3 1 so that with respect'to 2d orimary magnetic poles thissecondaq'" w has twelve circuits connected in 2 collector rings 33 andsimilarly twelve circuits connected in parallel between the rings 34.For the sake of clearness, onl the connections to the collector rings 33ave been fully indicated in the drawings. Every coil or group of coilsbeneath phase-belts p are 17 are connected in series to the similarlypositioned coil or group of coils six polesremoved with respect to the24-pole arrangement, and the terminals of these series connected coilsor groups of coils are connected to the collector rin s 33. The coilsbenzath phase-belts g an Q are similarly connected to the collectorrings 34. For the motor of 24 poles, there will, therefore, be twelve ofthese series-connected coils or groups of coils connected to each set ofcollector rings 33 and 34;. The transformer action between the lowresistance winding 31 and the high resistance squirrel cage winding 20is obtained by open-circuiting alternate sections of the primary windingembracing six adjacent poles.

It will be observed that the low resistance secondary winding 31 iseilectively opencircuited for a primary magnetic field of 24 poles. Thiswinding might, therefore, remain entirely inactive for this polararrangement and all of the secondary currentwould then be forced to flowin the high resistance winding 20. Generally, however, it will be moredesirable to provide external resistances 35 arranged to be connectedbetween collector rings 33 and 34, respectively, and thus to completethev circuits of the winding 31. The resistances 35 may be adjustableand when entirely out out so as to short-circuit the rings 33 and 34;,respectively, the winding becomes electrically equivalent to anexternally short-circuited' low resistance winding.

Although the winding 31 is efi'ectively open-circuited for 2 i-po es, itis internally short-circuited for either 16 or 32 poles. For the 16-polearrangement, the coils beneath phase-belts a, b and 0 are connected tothe collector rings 33 to form in efi'ect a short-circuitedstar-connected winding and the coils beneath phase-belts a, t and 2: aresimilarly connected to the collector rings 34:. For the 32-polearrangement, the winding is similarly a short-circuited, star-connectedwinding. The only difference between the short-circuits for the 16- and32- ole arrangements is that for 32 poles t e p and g circuits connectedto the collector rings 33 and 34, respectively, carry currents in thesame direction, while for 16 poles the currents in these p and qcircuits are 180 electrical degrees apart.

In Fig. 13 of the drawings, I have represented a modified arrangement ofconnections for such a system as illustrated in Fig. 9. The two 120degree (or 60) circuits of the generator winding 27 are independent andhave two terminals each brought'out to a six-unit generator switch 28.The two 30 degree (or 150) circuits of the enerator winding are alsoindependent an their four terminals are brought out to the switch 28. Afive-unit double-throw switch 29 is also provided. The phase-belts p,17, q and q of the pole arrangement of the motor of the system is asfollows: For g-poles with a quarter-phase source oi. energy, the

switch 29 is in its off position and the switch 28 is in its left-handposition. The arrangement of the twelve groups of the primary winding isthen substantially the same as in Fig. 10, the only difference beingthat the neutral point connections shown in Fig. 10 are not made in themotor of Fig. 13. For n-poles, the switch 28 is thrown to its right-handposition, and the switch 29 is thrown to its left-hand position. Thetwelve groups of the primary winding are arranged for this connectionsubstantially the same as represented in Fig. 11. For 2'n-poles, theswitches 28 and 29 are both in their right-hand positions, and oneterminal (A) of each phase winding of the generator is connected to thealternate corresponding phase-belts (a) of the motor, while 'theotherterminal (A) of the same generator phase winding is connected to theother corresponding phase-belts (a) of the motor. A diagram of theelectrical connections of the generator and motor circuits for 2n-polesis shown in Fig. 14 of the drawings. The same rotor as illustrated inFig. 9 may be used with the motor of Fig. 13.

I have herein shown and particularly de-' scribed certain embodiments ofmy invention for the purpose of explaining its principle and showing itsapplication, but numerous modifications of the details of constructionand arrangement of these embodiments and other applications will presentthemselves to those skilled in the art. I, therefore, wish to cover bythe following claims .all modificationslwithin the spirit of theinvention.

What ll claim as new and desire to secure by Letters Patent'of theUnited States, is

1. A multi-speed induction motor having a primary'winding arranged so asto produce balanced primary magnetic fields of. n

and pole numbers when supplied from three-phase and quarter-phasesystems oil energy distribution respectively, said primary windingcomprising a-plurahty of circuits each of which contains conductorswhich carry current relatively in the same ill) direction when theprimary winding is connected for either one of said diflerent polenumbers, said circuits being permanently connected for the n and polenumbers so that all the ends thereof, which are tobe connected to thesame phase of the threephase system-tor a pole numbers, are connectedtogether while the opposite ends thereof, which are to be connected tothe same'phase oi a quarter-phase system for pole numbers, are connectedtogether.

2, A multi-speed induction motor having a primary winding arranged so asto produce balanced primary magnetic fields cit a 3% and pole numberswhen supplied from three-phase and quarter-phase systems of energydistribution respectively, said primary winding comprising a pluralityof circuits each of which contains conductors which carry currentrelatively in the same way when the primary winding is connected foreither one of said difierent pole numhers, said circuits being connectedtogether so that all circuits which are to be connected to the samephase of a three-phase system for a pole numbers are permanentlyconnected together at one end while the opposite ends-oi said circuitsare connected so that all circuits which are to be connected to the samephase of a qu rter-phase system for ca pole numbers permanentlyconnected together,

3, A multrspeed induction motor having a primary winding arranged so asto produce balanced primary magnetic fields of a 3n and E pole numberswhen supplied i'rom :v three-phase and quarter-phase systems of energydistribution, said rimary winding comprising a plurality of circuitseach of contains conductors which carry current relatively in the samedirection when the primary winding is connected for either one of saiddifferent pole numbers, said circuits beinrpermanently arranged "for thea and. pole numbers so that there are three four terminals respectivelyfor the fit intense and pole numbers oi the primary winding whichrespectively term neutral points lor the mary windings. Y

4:. A multi-speed induction motor having a primary winding arranged soas to proand a pole numbers of the priduce balanced primary magneticfields of n and pole numbers when supplied from three-phase andquarter-phase systems of energy distribution respectively, said primarywinding compris ng a plurality of circuits each of which containsconductors which carry current relatively in the same way when theprimary winding is connected for either one of said difi'erent polenumbers, said circuits being permanently connected together so thatthere are three and tour terminals respectively for the a and 3;

pole numbers or the primary winding which 53 2 and a pole numbers of theprimary windmg,

v5, A multi-speed induction motor having a primary winding of themultiple layer drum type adapted to be connected as an a respectivelyform neutral points for the pole six-phase and as e5 2 pole quarterphasewinding when supplied' from threephase and quarter-phase systems ofenergy distribution, said primary winding having terminals, the numberof which does not ex- 7 ceed the sum oi the numbers oi phases of till377, I t -pole siX-pnase winding and as a e pole 2 quarter-phase windingand as a Qa-pole three-phase winding, said primary winding having lesstwelve terminals, and

means for controlling the connections of the generator winding and theconnections between said terminals and the generator arranged to connectthe terminals of said pri- 1 mary winding to, said source so as toproduce any one oi said polar arrangements or said primary winding.

. 7. A multi-speed induction motor having primary oi the multiple layerI drum type comprising twelve circuits, each of said circuits containingthose conductors which carry current relatively in the same way when theprimary winding is arranged 3% as an n-pole six-phase winding or as a 2ing is arranged to produce 1L or 2% primary magnetic poles whenconnected to a threephase source of alternatlng current energy and so asto produce primary magnetic poles when connected to a quarter-phasesource of alternating current energy.

8. A multi-speed induction motor having a primary winding of themultiple layer drum type comprising twelve circuits, each of saidcircuits containing those conductors which carry current relatively inthe same way when the primary winding is connected for any one of threedifierent pole numbers, said circuits being permanently connectedtogether so that the primary winding of the motor has less than twelveterminals, and means for connecting said terminals so that said primarywinding is arranged to produce primary magnetic fields of threedifferent pole numbers when suitably supplied with alternating currentenergy.

In witness whereof, I have hereunto set my hand this 29th day of May,1917.

CAMPBELL MACMILLAN.

